Well ladies and gentlemen, it looks like the summer heat is here once again! If you’ve been reading Trees Full of Money for a while, you’re probably aware of how passionate I am about the use of geothermal energy to heat and cool your home. Using energy stored in your own back yard, Geothermal Heat Pumps can save consumers 70% or more on their yearly heating and cooling bills, and best of all ground source heat pumps have a minimal impact on the environment.

Traditional Geothermal Heating and Cooling Systems are Expensive

Unfortunately, the cost of a professionally installed geothermal system is prohibitive to most homeowners. Complete residential geothermal systems can cost $20,000 to $30,000 or more depending on the application.

My Do It Yourself Alternative

Until such time that geothermal systems become less expensive (or I get a significant windfall of cash) I would like to share my tips on an alternative way to harvest geothermal energy to “partially” cool your home during those sweltering summer days.

This method has been utilized by many homeowners in the northern states for years without them ever realizing that they were tapping into a source of renewable energy. I have simply “perfected” the process to get the most efficient use out of the cool air that is stored inside your home’s basement.

If your home doesn’t have a basement or suitable crawl space beneath it, you will not be able to utilize this technique but you may be interested in reading about it anyway.

What Equipment You Need for My DIY Geothermal Cooling System:

A “Below Ground” basement or crawl space with direct access from inside your home (it also helps if your basement or crawl space has a small window that can be opened to add air flow).

A Portable Fan.

Optional: A Portable Dehumidifier

Why My DIY Geothermal Cooling System Works

During hot summer days and cold winter nights, basements in our homes stay relatively mild when compared with the outside temperatures and the temperatures in the main part of your house. This is a classic example of how geothermal energy works.

The temperature of your basements exterior walls are regulated by the relatively constant temperature of the radiant heat trapped only a few feet down beneath the ground adjacent to your home’s foundation walls. These temperatures radiated through your basements walls and cool (or heats) the air volume inside your basement. The trick is getting this usually damp and musty cool air distributed throughout the rest of your home.

After some experimenting, I have finally come up with the most efficient method for achieving this goal.

Setting Up My Do It Yourself Geothermal Cooling System

I place a small dehumidifier in my basement the night before to bring the relative humidity down from over 80% to less 60% by the following morning. I also ensure that all of the window shades are drawn on the “sunny side” of my house to minimize the effect of the suns “solar” heating. If your has a relatively low humidity then the use of a dehumidifier may not be necessary.

If the outside temperature gets below 75deg during the night I will leave most of the upstairs windows open in my house with fans sucking in the “cool” air until the outside temperature gets above this level.

As the sun comes up and the inside temperature of the house begins to rise I wait until the inside temperature of the house gets above 77deg. At this point I “turn on” my geothermal system by doing the following:

I crack open one of the small windows in my basement just enough to let a little bit of airflow through. Then (with all of the other windows closed in the house) I crack open another window in one of my homes upstairs bedrooms with all doors open between the two windows so that air can flow through (tip: opening the highest window you have in your home will vent out the most hot air in your home [heat rises!]). You can also close of other areas of the house that you do not wish to cool to maximize the cooling effect in the areas of the house you frequent during the day.

I then place a small window fan in an upstairs window with the flow of air pointing out the window. This technique effectively suck air up from the basement through the house and then out the window.

The trick is to monitor the temperature of the air on the suction side of your fan as it is being pushed outside. Close the windows (and the basement door) and shut the fan down when the drop in the rooms temperature begins leveling off.

It usually takes between 30 minutes to an hour for all of the cool air to be circulated through depending on your fan’s power and how large your home is. If all has gone to plan, the temperature inside your home should have dropped a more tolerable 4-5 degrees. This may buy you a couple of hours time that you don’t need to run your air conditioner.

Caution: If you run the fan too long, all of the cool air that was trapped in your basement will be displaced by the warmer outside which will then be sucked up into the rest of your home negating the whole process. You generally only get one shot at this cool air during the day since it will take at least 6 hours for your cool basement walls to regulate the temperature of the new mass of warm air that has been displaced into your basement.

It may seem like a lot of work but you really get the hang of it after a weekend of testing and if nothing else this DIY geothermal energy project is a fun experiment to share with your family! Thanks for reading and be sure to check out some of my other articles on personal finance, and alternative energy! I am also curious to hear how this technique works for you, be sure to comment below with any successes, failures, or criticisms of this method!

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Dude, Ben…That is Genius! I wonder how it will work in my house since I have a multi-level and all four levels are staggered. In other words, my house looks like a flight of staircases in a tall building. You go up one flight, you are on a landing, you turn and go up another flight, you are on a landing, you turn and go up another flight, etc. etc.

I don’t know about “genius”, but it is pretty cool to experiment with! I would pick which level of your house you spend the hottest part of the day in. Close off the other sections from that room and the basement and give it a shot!

This is a very creative tip. My parents have a basement that is the perfect place to hang out in the summer, sometimes you even need a blanket. Fortunately, it is a finished basement, so they can be down there during the day, and even sleep down there at night.

This is genius! I love it. I don’t have a basement, unfortunately, but I would try it at my parents’ house. One question though – will it work in reverse? Ie, heating the house? My guess is not, since the basement would still be cooler… ?

There will not be enough heat in the basement for this system to effectively work in “reverse” in the winter time.

And even in the summer time, you only have one shot to get it right. You should be able to keep your house cool for a couple hours longer without running the AC, but of course that depends on your home’s insulation properties, and the temperature outside your house!

Another idea would be to close all the cold air returns in your house and open the ones in the basement. The basement walls and floor will cool the air as it passes through and the furnace will blow the cooled air into the house just run your furnace fan only.

This will change your basement into the cooling device for your home instead of the A/c

also this doesnt allow any hot air from the outside in and it recirculates the air you already have cold.

You may need extra cold air inlets in your basemnet most new homes are ducted with efficiency and cold spots in mind so you need to help it along with some extra cold air intakes in the basemnt

I just did this in my house about an hour ago my crawlspace temp is maintaining at 68.9 degrees my house is 75 degrees and it is 86 outside i will give an update as to any temp changes indoors and outside it is about 4 oclock now so its the hottest part of the day here in central illinois

What you are doing is called “passive solar cooling” and homes could (actually should) be designed to take advantage of this. We are currently building a home in Florida which uses 600 linear feet of buried pipe to create underground airspace similar to the use of your basement for storing cool air. We are going a bit further with the use of thermal chimneys to create a gentle negative pressure inside the home which slowly draws cool air in from the underground tubes. This maintains a comfortable inside temperature even when blazing outside.

Hey Ben… I have considered doing something similar in a new construction. Using PVC pipe of 6″ or so size around the foundation then pipe it into the void beneath the AC closet so the negative pressure created by filtering will suck the air through the burried pipe from a wall vent hooked to the PVC pipe. Run the pipe as far as you can afford around the foundation and up into a wall then attach it through a duct box and cover with a decorative vent cover. possibly use light filtering material to prevent bugs or trash being sucked into the pipe.What does anyone think about that?

I have a 150 foot deep abandoned well on my property, I was thinking about using it as a shaft for passive geo cooling for a workshop area in my barn. It would draw in up to 100 degree air from outside (here in Texas), pass down the 150 foot shaft, then back up the shaft (in a separate 2″ tube) and into my 12×16 insulated room in the barn. If it doesnt work, I may add a cold water drip to allow evaporation to assist the cooling of the air down the hole. My concerns are wether I will be able to suck enough air back up through a 2″ pipe to cool a room that size – it is very well insulated. Would PVC be OK to use? Is 150 feet (300 feet total, since the air will go down the 4″ casing, then up thru the 2″ PVC) enough distance to achive ground temerature? If this works I may dig a trench 3′ deep around my property and make it about 300 ft long, and drop a 6″ pipe into the ground and simply cool the outside air with the ground and pump it into my house. Step 1 is to try the well, then step 2 would be to build the trench and shut down my AC units. I may have to create several trenches in order to cool the entire home, but, it will never wear out, never need repair -except for replacing the whole house fan on occasion. Probably cost me a couple grand if I do it myself. Much cheaper than a whole dual AC system, and the summer cooling bills should be pretty low. – it would just be the cost of fans to draw in enough air to keep the house cool.

The nature of your question goes beyond my level of expertise in the area! However, perhaps some other readers on this site will be able to answer your question! Let me know how your DIY geothermal system works out!

mother earth magizine from the early 80’s had an article on this exact use. I have been wanting to try it for years but did not have the nerve. I think 6 feet was required depth and I think 300 feet in length, but not sure. ie the temperature is the same from 6 feet or lower. Not sure of the size of the diameter of the tube. I live on 3 acres with plenty of room to dig but don’t want to spend the money for failure. I would appreciate any input.

I don’t understand the pre-occupation with buried or subterranean air-vent pipes.

It would be much cheaper and healthier in the long run to run PEX water pipes underground in the back yard, in a closed-loop system. Caution: pipes have to be buried at least SIX feet deep; going deeper appears to provide a little cooler environment at a much higher cost. Use a small pump (low watt) to circulate the water through a large radiator (new or old), and blow air through the radiator. Be prepared to pipe condensate from the radiator into a drain, either outside or into the sanitary sewer.

If you have a well, fine. But please don’t go for the excessive cost (we were offered) to bore THREE thirty-inch wells 100′ deep to cool your piping, to provide 3-ton AC capacity…..this by a NW Florida geo-thermal “expert” company.

The air-movement fan and pump can be thermostatically c0ntrolled. The radiator can be enclosed in a foam-board plenum (use dry-wall screws and good duct tape to construct and seal) and air can be distributed by existing (or new) air ducts. Filter the air where it goes into the plenum to keep the radiator clean.

Or, you can build (new) a super-insulated home with AAC (Aerated Autoclaved Concrete) walls and and insulated roof (poly-iso), like we are doing in Southern Alabama. We will simply install the radiator in the attic and air-cool the entire structure, with bleed air (from the plenum) to cool the hurricane room and garage. No duct-work, except to the hurricane room and garage. Radiator will be mounted high in the attic, in an open-ended plenum, and, guess what, cool air will drift down through ceiling vents into the house. There will be two return air vents installed (at either end of the house), near the ceilings where some stratified warmer air will collect to return air back to the radiator plenum. There will also be a “fresh-air” vent from the outside into the return air duct to the plenum. These will provide the needed air “circulation feeling”, as well as the use of exhaust fans in the kitchen, two bathrooms and laundry room.

We’re building a 1700 square foot home with attached 400 square foot garage. On a warm Summer day of 90+ degrees, ground temperature at -6 feet is 58-64 degrees here (depending on accuracy of my measuring equipment (64) versus local wisdom (58). Insulated chases have been built into the back walls of the house to minimize coolth loss. Best estimates from much internet searching look for 100′ buried 3/4″ PEX per ton of conditioning. Our super-insulated home requires a “normal” two-ton HVAC system. We are going to be very conservative and bury 500′ of PEX, which is probably over-kill.

We also are using radiant floor heat, so we are not concerned about “mixing” systems, although the 58-64 degrees sure does give one a leg up on a “basic” warming source, if you were using a “normal” ducted air system. But, our basic premise is this: cool air falls (so we’ll start high in the attic with this source) and warm air rises (so we’ll have Pex hot water in the floor). This type of split operation is the most efficient use of normal air circulation.

For those of you who may doubt the value of super-insulating a building, consider these facts: We have completed the 400 square-foot garage walls with AAC block and (so far) R-30 built-up roof, with steel shingles.
On June 5, 2009, at 1PM CDT, sky was clear with 86-degree outside (shaded, protected) temperature (sunlight actually measured 110 degrees). Inside the garage, with no doors and no windows installed (basically an open structure with NO roof vents), the temperature measured 79 degrees (outside and inside measurements were taken about 3′ above the floor). These temperatures were confirmed by a visiting building contractor. We personally have observed similar measurements in two other open AAC buildings (no windows or doors installed).

But, try and find information for this type of installation on the internet! Good luck! The whole geo-thermal idea has been hi-jacked by companies who want to sell you heat-exchangers and add-on hot water equipment, all at big-bucks prices.

Good luck with your project. Just watch out for mold and fungus in those air-tube circulation systems!

Are you really saving anything? Seems to me running a dehumidifier for 7 hours the night before in the basement and a fan all night long is simply a trade off for running the A/C.
Even if you do cool the house by 4 or 5 degrees as you say, leaving the windows open and pulling the air up from the basement(dehumidifier or not) when the A/C does come on it has to deal with the responsibility of removing the humidity from the air before comfortable temperature change can occur. Seems to me your just robbing Peter to pay Paul.

What if you connected your pump adn water pipes to a prexisting exchanger in the house? I have a A/C compressor outside that will die in a few years. If I merely change out the freon in the lines for water attached to a geothermal closed system, would that work? I see here that 6′ seems to be the magic depth. I’m planning on doing some temperature checks this summer to see what the actual differential is at 2-8 feet deep.

28 x 32 rectangle cabin…crawl space underneath…please clarify…for a simple measure…the question is: if I bury about 6′ deep into a trench about 300′ of 3″ PVC pipe, and provide a filter on the top-ground side, and then blow that air into the house through duct work in the crawl space, I should see significant cooling benefit? What about toxicity of air? Live in Texas, no shade trees around cabin, lots of open space, temperatures in July-Sept. can be 100 plus outside.

I run a small window air conditioner in a basement window. This dries it out like a dehumidifier but, puts the hot air outside. Then we run our furnace fan to circulate it.
Works good we can run our blower real slow.

I was a floor installer working in this new house that was on a hill. I went down to basement to find electric and noticed a 5 foot hole in the wall with screen over it. When homeowner showed up I asked him about this. He said he was a engineer and he said this is the way people stayed cool and warm in castles. He said house had to be on a hill and a tube from basement wall had to go 60 feet under ground below freeze level and came out of ground 60 feet away of a 12 inch hole with screens on both ends to prevent animals from entering house. Once complete a attic fan was installed and turned on it would draw cold or hot air in by attic fan and by going through 60 feet of tubeing by the time it entered his house it would always be 60 degrees because under ground it always stayed at 60 degrees. When he built his house he did the duct work from his basement to suck up the air from attic fan to cool the house. no cost heating and cooling. not sure what castles used to draw air in like a attic fan but made cents. only electric cost was use of attic fan of coarse 60 degress is kinda cool either way. maybe he used heat to bring it up to 8 more degrees either way? Still a way to beat gas and electric companies from charging too much.

Terry
What you discribe seems like an easy and very enexpensive way to go. I think the ground temp.is probably closer to 50 deg. But when you look at the delta of an additional 18 to 20 deg verses having to go 40 to 50 deg. the benifit is obvious. This would allow a homeowner to opt for a much smaller heating system to augment the diffrence required. Rather than having to run all that pipe it may work just as well with one large cement tank like those used in septic systems filled with large stone with an inlet pipe and an outlet. What is a little curious is why this is not being done. Seems like a one week project. that in the worst case would help lower home heating costs.

I was happy to see that I’m not the only one who cools with basement air!! I leave my crawlspace door open and put a fan at the bottom of the stairs “pointing up” – this pushes the air up the stairs. Then, I have a fan at the bottom of my house stairs doing the same thing. Upstairs I have 2 window fans pulling the air out (I just turn my boxfan backwards). I also use smaller fans around the house when it’s really hot (circulating the air helps with cooling), pull the drapes on sunny windows and keep the doors closed. It works great. I don’t open a window in my basement but I do have a dehumidifier that runs on automatic. I thought about putting in a whole-house fan, leaving the basement open and everything else closed. But I’m not really familiar with whole-house fans and don’t know if that would work.

Have you tried making a passive solar heater? That is going to be my next project.

Anyone here have any comments about what I am considering for cooling a rock cabin in the heart of Texas where summer temperatures are now 100+ daily. The ground is seriously rocky so trenching to 6 foot for hundreds of feet is near impossible or cost prohibitive. The rock walls of my cabin are 16″ thick above ground and 24″ below ground. The walls go down into the ground around 3 feet around the home. I may bring in more soil and bank it against the lower exterior walls to gain another foot or so of depth around the cabin. The interior of the cabin is filled with about 8-10 inches of a caliche type soil where I will bury drainage pipes etc.. Later I will pour about 4 inches of cement on top of all this.

My thought is to simply bury copper pipe inside the home and below the caliche soil layer and circulate water/refrigerant to a radiator cooling fan inside the cabin. Considering that the walls of the cabin are thick and mostly shaded I am thinking that the soil beneath the cabin will remain relatively cool in summer (around 68 deg) and the copper pipe will conduct this easily.

Nice idea, but I think the warming effect on the floor will be greater than the cooling effect in the air.

The copper pipe running through the “cool” floor of your cabin will not have as much “surface area exposure” than if it were run underground for “hundreds of feet” as is often done with conventional geothermal installations. You may have a decent cooling effect at first, but after a short while the liquide will be warmed up by the radiator and circulated back into the ground brining the temperature of the floor up (from 68 deg to perhaps 80).

I have always wanted to better understand geo-applications for energy efficiency of climate control in residential homes. So, thank you all for sharing your experiences and opinions.
I wanted to share my own experience based on my own engineering.
I have a well on my property that is of no use to our home (county water) other than watering the flowers and such. I noticed though that the temperature of the water was very cold (about 50F) and immediately thought this would make for a good cooling source if I could harness it.
A neighbor was tossing out a window A/C unit and this was exactly what I needed for parts.
I salvaged the air handling unit and the evaporator core for my geo-cooling experiment. Passing the cold well water through the evaporator would basically bypass the need for the compressor as the source for the refrigerant.
Long story short, phase 1 is cooling my moderately sized home. I am drawing 70F air in and expelling 60F, thus cooling the home quite nicely when the outside temperature is above 85F. The water from the well is entering the evaporator radiator at about 50F and leaving at about 55F.
Currently I am sending the water back out to the well using a garden hose and using the well pump as my circulator.
Phase 2 would add thermostatic control using an electric (24VAC) lawn sprinkler valve to control the water flow.
Phase 3 will be to drop a copper tube heat exchanger down into the well and use a hydronic pump for circulating (mostly) water in a closed circuit. Lucky for me I work in the copper business and have ready access to tubing made specially for liquid-liquid heat exchange, thus giving me a very high efficiency for cooling the water back down to the well water temperature.
I will post my progress as it happens…

We have 3 large solar panels on our roof. They are about 25-30 years old. They were part of a water heating system which is defunct (bladder on the tank broke and the system was disabled). I wondered if we could take the panels off the roof, put them on the south side of the house and “somehow” use them as passive solar heat. Any thoughts?????

The furnace fan will distribute the cooler air throughout the ductwork just as well. It takes about 10 min for a good exchange in a two storey home then the fan must be shut off so it doesn’t start pushing the exchanged air thro the system.

Hi Ben, thanks for this site, you and other guests have given me additional ideas and info to my similar goals. I have my basement edges jackhammered out – about 1 foot opening around to add a drain pipe to the sump. I realsied i was half way there with cooling and was curious which would be the better option, to run 6 inch pipes under the cemend floor and around the basement for air circulation, or run PEX with a closed water circulation system – i would then send the air of either one into the air ducts of the house. Thank you for any advice!

Hi! Cool air always downs isn’t it… Let’s not let it to flow outside of the house with a window fan and instead of that lets find a pipe that long enough from basement to highest floor of our house and find a smaller fan on its mouth. We will take the cool air from the basement and will give it to the top floor of our house. Cool air will be down in our house till getting into the basement again… All doors are open but windows not! Basement will make the air cooler than the air taken from outside basement window… there will be balance between the basement temperature and rest of the house (heat will be balanced between cool and hot in whole house). What do you think about this?

I think you may be on to something with your pipe from the basement. My only question is, “How would you remove the hot air which will rise to the top floor of the house?” Wouldn’t you need to exhaust it somehow?

Suzi

PS I made the passive solar heater with soda cans. It seems to have raised the temp of the bedroom 2 degrees on a sunny day with the bedroom door open. I will try it tomorrow with the door closed and see if it raises the temp any higher. However, maybe just opening the blinds on the south facing window would have done the same thing. It was fun making it and it does keep the cold air from the window out at night.

DIY geothermal can be done. DIY for 10 cents on the dollar, or be rich.
We rented a portable drilling rig, got info from http://www.drillcat.com
They told me where to get loops and also provided DIY books, i got the water well drilling and troubleshooting book. Our geothermal system took 8 days to do, but saved 38k.

Geothermal DIY can be done, we did it. Major cost was drilling. we should have bought or rented a drillcat drilling rig. Thanks for the great link, very helpful, and simple straight forward help, no frills, down to where the rubber hits the road simple. We are now looking into a Good used rig for several water wells for our close family, on 3 tracts of land.

I have an Idea for a heating and/or cooling booster. I could use a ditch witch to dig a 100 foot long loop-shaped trench away from the house and bury a roll of 4″ black plastic corrugated tubing in it. I think the ditch witch digs down 4 feet. Each end of the loop of plastic tubing leads into the house. A small fan in one end of the tube draws household air through the 100 feet of buried tube back into the house. I think that after the air is drawn through the tube it should be the temperature of the ground, or at least close to it. Has anyone tried this idea?

It’s my understanding that a dehumidifier is simply and Air Conditioner that heats back up the air. As such, it would be smarter to run an AC than a dehumidifier. With that understanding, it would make sense to run the AC in the hottest part of your house at night.

It might cost the same and you’d get a cooler room. Then again, maybe I’m totally wrong — certainly worth testing. Just be sure to use a window AC unit or at least one that vents hot air outside. There are units sold now that cool one room while heating the other which is lame. You can tell those because they don’t have two vents, one for intake and one for exhaust.